Insulin levels control female germline stem cell maintenance via the niche in Drosophila.

Stem cell maintenance depends on local signals provided by specialized microenvironments, or niches, in which they reside. The potential role of systemic factors in stem cell maintenance, however, has remained largely unexplored. Here, we show that insulin signaling integrates the effects of diet and age on germline stem cell (GSC) maintenance through the dual regulation of cap cell number (via Notch signaling) and cap cell-GSC interaction (via E-cadherin) and that the normal process of GSC and niche cell loss that occurs with age can be suppressed by increased levels of insulin-like peptides. These results underscore the importance of systemic factors for the regulation of stem cell niches and, thereby, of stem cell numbers.